Our ultimate goal is to obtain an analytic understanding of auditory perception and speech reception in the hearing-impaired and to develop improved diagnostic procedures and prosthetic devices for the hearing impaired. The research proposed in this application is concerned with the ability of subjects having sensorineural hearing impairments (as well as subjects with normal hearing and with simulated losses) to discriminate spectral shape, and involves both experimental and theoretical work. Spectral shape perception has been chosen as the focal point of this research because of its importance in the perception of speech and music, and in the acquisition of environmental information, and because an increased understanding of spectral shape discrimination will constitute a significant advance in the general field of auditory science. Discrimination has been chosen as the task to be studied because performance in this task is more closely related to peripheral processing than performance on other tasks (such as identification or scaling). The proposed experimental research includes measurement of spectral shape discrimination for synthetic abstractions of steady-state voiceless fricatives and the burst portion of voiceless plosives using a roving-level paradigm to eliminate loudness cues, measurement of the masked detection of tones with the synthetic stimuli (and filtered versions of the synthetic stimuli) serving as maskers, and measurement of intensity and frequency discrimination for tones. The proposed theoretical work involves the specification of a peripheral processor (for frequency analysis, measurement of channel activity, internal noise, etc.) and the specification of a central processor (for level normalization, formation of decision variables, selection of decision criterion, etc.) that are adequate for interpreting results on both normal and impaired listeners.